This invention relates to electrical switches and more particularly to electrical solenoid switches in which a switch operator is caused to move by electromagnetic coils in order to make or break a circuit. In particular, the present invention relates to a solenoid switch which is positively actuated in two directions by a solenoid arrangement and has a capability of manual operation in one direction.
In certain switch applications, it is necessary that assurances be had that equipment containing a switch not be used unless such use is indicated. It may be further important that the switch be tamper proof to the extent that unauthorized personnel cannot turn the equipment on and, when the equipment has been turned on, the equipment cannot be turned off except under certain circumstances. It is also desired that a switch be able to be manually set at and locked into an "off" position, with a visual indication of the locked "off" condition being present. In addition to the indication of the locked "off" position, it is important that a visual indication of the switched state of the switch be provided. For example, if personnel are working in an area where inadvertant operation of the equipment is hazardous, positive assurances of "safing" must be had.
In enhancing the reliability of such switch units, it is important that the switch be able to be operated reliably for a large number of cycles without preventative maintenance. The switch must have arc suppression capabilities. The use of an arc suppression circuit must be avoided because of the possibility that circuit elements within the arc suppression circuit can fail either on their own or with the aid of tampering. Arcing and other contact wear factors become more significant when high current levels, such as 50 amperes, are switched. The effects of pitting and other types of wear on the contact surfaces must also be minimized. Furthermore, these arc suppression problems become magnified in outer space environments in which a vacuum is present.
In further enhancing the reliability of switching, it is important that other switch malfunctions, such as contact bounce and undesired switching be eliminated. This becomes difficult when the switch becomes subjected to external forces, such as forces of acceleration and shock forces.